The present invention relates to non-ferrous metallurgy, and in particular it relates to high strength alloys of Alxe2x80x94Znxe2x80x94Mgxe2x80x94Cu system used as a structural material for main parts in aircraft (upper skins and stringers of the wing, loaded beams, etc), in rocket-, transportation and instrument engineering.
Well-known are high strength aluminium-based alloys of Alxe2x80x94Znxe2x80x94Mgxe2x80x94Cu system additionally doped with a minor amount of zirconium.
The Russian alloy 1973 has the following composition (in weight %):
The American alloy 7050 comprises (wt %):
Also is patented the American alloy comprising (wt %):
The common disadvantage of all said alloys is the unsatisfactory level of static strength and specific characteristics which doesn""t allow to improve service properties, to increase the weight efficiency of the articles aiming to raise carrying capacity, to save fuel, to increase flight distance range, etc.
The American alloy is suggested comprising (wt %):
and at least one element from the group including
Said alloy has the following disadvantages:
high and superhigh strength is mainly achieved by heavy alloying with main elementsxe2x80x94zinc, magnesium, copper (their maximum sum  greater than 13.0%), but the increased amount of copper leads to the reduction of ductility, crackxe2x80x94and fatigue resistance;
the additional alloying with expensive elements (hafnium, vanadium) is used, and that leads to the increase in cost of semi-finished products and finished articles, especially when there is a large-scale production and the products are of large sizes;
the alloy has the unsatisfactory ductility in as-cast condition (and therefore has the tendency to appearing of cracks in ingots especially large-sized ingots which are cast from such alloys with difficulty) and under the deformation of semiproducts;
the alloy""s composition doesn""t provide the optimum conditions of the microstructure formation and service characteristics of such members as skins and stringers of the wing which are needed for modem and future aircraft.